As disclosed in Japanese Unexamined Patent Application Publication No. 2005-341684 (to be referred to as Patent Document 1), forming a laminated core with an annular yoke by laminated core segments each having a yoke-segment section and a magnetic pole has facilitated wire windings around magnetic poles of a laminated core and has enhanced the winding density. Each of core segment sheets to form the laminated core segment has a convexity and a concavity to be fitted therein formed at both sides in the radial direction thereof. The convexity is made by oblique cuts at a side of a yoke-segment piece, one cut starting at a point on a radially inward brim at the side of the yoke-segment piece, the other cut starting at a point on an outward edge. Then, sets of one type of the core segment sheets and sets of the other type of the core segment sheets, each sheet having the convexity and concavity, are laminated alternately thereby to form the laminated core segment with first and second joining sections formed at both sides thereof, and the plurality of laminated core segments are connected in a ring shape at the first and second joining sections.
However, the laminated core disclosed in Patent Document 1 is provided with magnetic pole shaft sections each having a rectangular cross section, which damages the wires. Additionally, it is difficult to bend the wires completely perpendicularly at the corners of the magnetic pole shaft sections; thus, spaces are formed between the wires and portions except the corners, thereby lowering the winding efficiency (space factor). Meanwhile, Japanese Unexamined Patent Application Publication No. 2005-348553 (to be referred to as Patent Document 2) discloses a laminated core provided with magnetic pole shaft sections 200 each having a width gradually decreasing at an upper laminated portion 201 in an upward direction and at a lower laminated portion 202 in a downward direction as shown in FIG. 14. According to this method, the wire can be wound around the magnetic pole shaft section 200 without producing spaces at upper and lower ends thereof. The reference numeral 203 designates a core segment sheet.
According to the art disclosed in Patent Document 2, the upper and lower ends of the magnetic pole shaft section 200 have no sharp edges, thereby facilitating smooth wire winding without producing spaces. However, upper and lower ends at radially outward sides of the magnetic pole tooth section 204 located at the end of the magnetic pole shaft section 200 have substantially right angles and sharp edges. As a result, the wires (not shown) wound densely around the magnetic pole shaft section 200 are in close contact with each other, which breaks the insulation coatings of the wires.
In addition, the magnetic pole tooth section 204 is larger than the magnetic pole shaft section 200 and positioned closer to a winding machine. Thus, when wire is wound around the magnetic pole shaft section 200, the wire comes into contact with the magnetic pole tooth section 204, which damages the wire insulation coating or the wire itself. This is liable to occur when the wire is wound at high speeds, which inhibits the improvement in productivity of the winding operation.
According to Patent Document 2, the radial thickness of the magnetic pole tooth section 204 is extremely reduced toward both ends in the circumferential direction, which increases flux decay at both sides of the magnetic pole tooth section 204 thereby to lower the magnetic efficiency. Furthermore, according to Patent Document 2, because the core segment sheets configuring the laminated core segment are punched from the same direction, downward punching burrs 205 remain at the corners of magnetic pole shaft pieces laminated in the lower portion of the magnetic pole shaft section 200 around which a wire is wound. The downwardly projecting punching burrs 205 damage the wire.
Moreover, according to Patent Document 2, a semicircular convexity and a semicircular concavity are formed at both sides of each core segment sheet except at radially outward and inward edges thereof. The core segment sheets are laminated to form the plurality of laminated core segments with joining sections including linear convexities and linear concavities, and the laminated core segments are connected annularly by the joining sections.
However, the linear convexity and the linear concavity are only fitted with each other, but do not produce a restraining force to be applied in the laminating direction. Accordingly, adjoining laminated core segments move vertically, and in some cases, the connected laminated core segments are bent at the joining sections and liable to break apart.
On the other hand, according to Patent Document 1, each of the core segment sheets has the convexity and concavity formed at the full radial width of the yoke-segment piece, and the sets of the core segment sheets of one type and the sets of the core segment sheets of the other type, each set consisting of a plurality of sheets, are laminated alternately to form the laminated core segment having the first and the second joining sections at both ends thereof. However, since the joining sections have no radially extending planes, it is difficult, when two to three laminated core segments are connected, to visually examine from outside if the first and the second joining sections are engaged surely. Consequently, the convexity is fitted in the concavity at a slight tilt, bringing about an inaccurate joint between adjoining laminated core segments. In particular, if dust or the like enters the concavity, or the convexity is damaged, the defective joint between the concavity and convexity occurs.
The present invention has been made under such circumstances and the objects of the present invention are to provide a laminated core that ensures: (1) efficient wire winding around a magnetic pole shaft section at a high space factor without damaging the insulation coating of the wire or the wire itself, and (2) accurate and easy assembly of laminated core segments, and to provide a method of manufacturing the laminated core.